Resilience of soybean genotypes to drought stress during the early vegetative stage

Authors: NARAYANA, NISARGA - Mississippi State University; WIJEWANDANA, CHATURIKA - Mississippi State University; ALSAJRI, FIRAS - Mississippi State University; REDDY, K. RAJA - Mississippi State University; Stetina, Salliana - Sally; BHEEMANAHALLI, RAJU - Mississippi State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/17/2024
Publication Date: 7/29/2024
Citation: Narayana, N.K., Wijewandana, C., Alsajri, F.A., Reddy, K., Stetina, S.R., Bheemanahalli, R. 2024. Resilience of soybean genotypes to drought stress during the early vegetative stage. Scientific Reports. 14:17365. https://doi.org/10.1038/s41598-024-67930-w.
DOI: https://doi.org/10.1038/s41598-024-67930-w

Interpretive Summary: Drought stress poses a significant risk to soybean production. Exposure to brief dry periods during the first month of plant growth can have a negative effect on soybean development. This study focused on characterizing 64 soybean lines for traits associated with drought tolerance during the early vegetative stage. Soybean cultivars were exposed to two soil moisture treatments, 100% evapotranspiration (well-watered) and 50% evapotranspiration (drought), under controlled growing conditions. Eighteen traits related to the size and function of roots and shoots were measured. The data were analyzed to determine if any of the traits were closely related to drought tolerance and if they could be used to select soybean lines with superior drought tolerance. In general, drought stress increased root weight and decreased shoot weight, resulting in higher root-to-shoot weight ratios in soybean lines more susceptible to the effects of drought. Only two of the 64 soybean lines tested, S55-Q3 and R2C4775, had balanced root-to-shoot ratios and were identified as being drought tolerant. Although drought tolerance was not common in the set of lines tested, those that possess this trait may contribute to the genetic improvement of drought tolerance in soybeans if used as parents in breeding programs. Evaluation of root-to-shoot ratios can help soybean breeders select additional lines for use in their crop improvement programs, and may help crop consultants or extension agents assist growers in selecting the most drought tolerant lines from those commercially available for immediate use.

Technical Abstract: Drought stress poses a significant risk to soybean production, which relies on optimum rainfall. However, exposure to brief dry periods during early vegetative growth seriously impacts soybean growth and development. Therefore, this study focused on characterizing 64 soybean cultivars for traits associated with drought tolerance during the early vegetative stage. Soybean cultivars were exposed to two soil moisture treatments, 100% evapotranspiration (well-watered) and 50% evapotranspiration (drought), using the Soil-Plant-Atmosphere Research (SPAR) units. A total of 18 morpho-physiological, shoot, and root-related traits were evaluated. Under drought stress, significant variations were observed among the soybean cultivars. Moisture stress significantly increased root weight, root volume, and root-to-shoot ratio but reduced all tested cultivars' shoot weight and root length. Overall, plant growth was diminished under drought stress. Drought increased the canopy temperature by +3.1 °C, possibly due to inadequate moisture levels to meet the evapotranspiration demand. The combined drought response index (CDRI) was associated with the root response index, while it showed poor association with the physiological response index. These findings demonstrate that a balanced root-to-shoot ratio can determine phenotypic differences in drought tolerance in soybeans. The cultivars S55-Q3 and R2C4775 are associated with better root and shoot growth under drought stress at the early vegetative stage, thereby contributing to the drought tolerance in later stages. These lines may contribute to the genetic improvement of drought tolerance in soybeans if used as parents in breeding programs.